Regular use of sunscreens with SPF greater than 15, significantly reduced the risk of melanoma in a large cohort of average-risk women, investigators reported.
Melanoma is a type of skin cancer that can spread to other organs in the body, unlike basal cell carcinoma which rarely leaves the site.
Reza Ghiasvand, of the University of Oslo in Norway, and co-authors and colleagues analyzed data from the Norwegian Women and Cancer(NOWAC) study, initiated in 1991. The NOWAC population came from a random sample of more than 300,000 Norwegian women age 30 to 75, identified through the national population registry.
On the basis of questionnaire responses, study participants were classified as sunscreen nonusers, users of sunscreens with SPF <15, or users of sunscreens with SPF ≥15. Participants were further classified into sunscreen use categories by high and low altitudes.
During a mean follow-up of 10.7 years, 722 study participants developed melanoma. Mean ages at the start of follow-up and melanoma diagnosis were 53 and 60, respectively.
Women who used SPF ≥15 sunscreens had a 33% reduction in the relative risk of melanoma compared with women who used sunscreens with lower SPF ratings. Regular use of SPF ≥15 sunscreens could reduce the risk of melanoma by about 18% among women ages 40 to 75. the findings are reported online in the Journal of Clinical Oncology.
"These prospective data support the hypothesis that during intentional sunbathing, use of SPF ≥15 sunscreen can reduce melanoma risk compared with use of SPF <15 sunscreen," the authors concluded. "Moreover, use of SPF ≥15 sunscreen by all women age 40 to 75 years could lead to an 18% drop in melanoma incidence in approximately 10 years."
Asked to respond to the findings, the American Academy of Dermatology had no comments specific to the study but referred to the organization's support for a "broad-spectrum, water-resistant sunscreen with an SPF of 30 or higher."
The trial involved a population of adults living in an area with high ambient solar radiation and high awareness of skin cancer risk, the authors continued.
In contrast, populations in Northern Europe have high exposure to ultraviolet radiation only during the summer, and the exposure often is intentional, as occurs with sunbathing. Whether sunscreens protect against melanoma in that type of population remained unclear.
Intriguingly, there was some conflicting evidence which showed some people who never applied sunscreen had a lower risk of skin cancer than those who wore low-factor sunscreen. The finding was expected, given the heterogeneity of sun exposure between the two groups, the authors noted.
Ghiasvand and colleagues estimated that the population attributable fraction (PAF) for melanoma associated with use of sunscreens with protection ratings of SPF ≥15 was 18%, if all women 40 to 75 used the sunscreens. The PAF increased to 21% for women with blond or red hair. For users of SPF <15 sunscreens, switching to SPF ≥15 sunscreens was associated with a PAF of 33%.